Fried rich, JOHANN

D.D., b. 1836. Prof. at Munich since of Friction were enunciated by Coulomb 1781 and confirmed | 1865; a ociate of Dr. Döllinger in the Old Catholic movement. by Marin 1830. They are: 1, friction is proportional to the intensity of normal pre ure between the surfaces ( i.e. , pre ure per unit area); 2, it is independent of the surface area in contact; and 3, of the velocity of the surfaces in contact. These laws are found to be true practically only within certain limits. Again, when the surfaces have been in contact a long time, the action of the surface layers of molecules upon one another is so far changed as to very considerably increase the co-efficient of static friction u. The co-efficient of kinetic friction is somewhat le for high velocities. The friction of motion is le than that which exists when the body has to be started from rest. Lubricants fill the interstices and keep the contact surfaces apart. The following are some of the usual co-efficients of unlubricated friction: cast iron on cast iron.15, wrought iron on wrought iron.14, bra on bra 20, wrought iron on cast iron.19, bra on iron.16. For lubricated friction it is difficult to formulate laws. When thick unguents are used, as for heavy pre ures, a resistance is offered by the lubricant to motion upon the surfaces, corresponding somewhat to fluid friction. For light pre ures and limpid lubricants, differences result from different methods of supplying the latter. It would seem from recent experimentation that the following values could be depended upon: light pre ures, 30 to 40 lbs. per sq. in., 300 fpm., from.01 to.04; heavier pre ures, 100 to 500 lbs. per sq. in., from.02 to.10 (fpm. = feet per minute). Ch. History of Germany, 1867-69; Vatican Councils , 3 vols., 1877-87; Jesuits, 1881.